Computer starts but wont post

[GGYUC]

My computer (which has been working for almost 3 years), recently started playing up.
When I turn the computer on, nothing else seems to be interacting with it (i.e. the monitor wont turn on, the keyboard and mouse wont light up)
So to trouble shoot this, we
- turned it off and on in a variety of different ways
- removed the gpu (The computer worked properly)
-removed the left ram stick (the computer worked properly)
-remove the right ram stick (the computer worked properly)
-did the above but switched the ram sticks around (the computer worked properly)

In short, If one of these components are unplugged (GPU/RAM) the computer works properly.

But when we reinstalled one of the RAM sticks (so everything was plugged in properly) the computer worked, but only for about 3 restarts before it started the problem again.

if you have any suggestions i would be grateful.

P.S. we believe this might indicate a problem with the PSU, but some research on other forums say that it could be the motherboard

SPECS
CPU: Intel 4790K i7 4 GHz LGA1150 8MB
MOTHERBOARD: Gigabyte Z97X-Gaming 3
GPU: 4GB GTX 760
RAM: G.Skill Sniper 8GB DDR3 * 2
HDD:Seagate 3.5" Barracuda 3TB
SSD:Kingston 240Gb SATA3 2.5"
PSU: Corsair CS750M

 

[brispuss]

Try another known working PSU, and/or try the present PSU in another computer.

 

[GGYUC]

Try another known working PSU, and/or try the present PSU in another computer.

We dont have another PSU Or another PC

 

[brispuss]

Borrow/use a friend or neighbor's etc. PSU or computer for the test.

Since testing motherboards is difficult, eliminating or confirming that the PSU is the cause of the issue is the best way to go. Unless you want to and can try another motherboard?

 

[GGYUC]

I shut down the PC (it only has one ram stick in it still) and it didnt restart properly (wouldn't POST)
after we tried a couple of restarts
we Switched the position of the RAM and now works again, starting to really confuse me

 

[GGYUC]

Another bit of information, when the computer starts properly it doesnt randomly shutdown while in use (or sleeping). This might mean its leaning more towards a fault in the mother board but im not sure?

Also Ill add the Specs of the PC to the OP

 

[GGYUC]

Borrow/use a friend or neighbor's etc. PSU or computer for the test.

Since testing motherboards is difficult, eliminating or confirming that the PSU is the cause of the issue is the best way to go. Unless you want to and can try another motherboard?

We also live in an area (rural) where its difficult to get our hands on a PSU to borrow. The computer sometimes starts an infinite restart cycle as well, which can also be fixed temporarily by reseating the RAM. We also want to know if its possible to hot swap RAM, to test if the PSU will run dry while its all components are in, this could lead to the problem being the PC is not getting enough power on startup or something faulty in the motherboard.

 

[brispuss]

Don't swap memory while the computer is running. There is a risk of (further) damage to memory and/or to memory slots doing "hot" swaps.

Sorry, but can't think of another way to test apart from trying another PSU, or trying PSU in another computer, or trying another motherboard.

 

[GGYUC]

Don't swap memory while the computer is running. There is a risk of (further) damage to memory and/or to memory slots doing "hot" swaps.

Sorry, but can't think of another way to test apart from trying another PSU, or trying PSU in another computer, or trying another motherboard.

Thanks for your help, we are arranging another motherboard to test but if anyone else has any suggestions that would be helpful.